>>> good morning, america. breaking news overnight, a third explosion and a fire at japan's nuclear facility. all four reactors, now critically compromised, as japan stands on the brink of a nuclear catastrophe. hundreds of thousands ordered indoors, as radiation levels spike. contaminated citizens isolated from their families. as tokyo braces for the fallout, could america's west coast be at risk? >>> and new images of the tsunami's force and fury. residents, percent perched atop trucks. clinging to survive. in its wake, entire destruction. a sign of hope, though. 9,700 feared dead, now found alive. diane sawyer is on the ground, leading our team, as japan continues to face an unprecedented disaster. >>> and good morning. we want to get right to the latest on that nuclear crisis that took an ominous turn over night. >> even worse than we thought. >> much worse. another explosion and a fire at those reactors. japan's prime minister pleaded for calm. but warned of more radiation leakage. and other officials, bot